The invention relates to a knitting machine, especially a circular knitting machine, with at least one knitting tool carrier in which there are mounted displaceably knitting tools with a needle distance t, with a knitting cam assembly assigned to the carrier for guiding the knitting tools, the carrier and the knitting cam assembly being moveable relative to one another and the knitting cam assembly containing a plurality of systems lying one behind the other in the direction of movement, which systems having respectively a first and a second selection point, lying one behind the other in the direction of movement, with one electrically controllable selection member respectively, with a timing signal-generating device for producing timing signals in temporal intervals corresponding to the distance t and with a programme control device coupled with the timing signal-generating device for emitting electronic control signals for the control members.
Knitting machines for producing patterned knitwear are provided with a multiplicity of selection points, on which selection members are frequently arranged which are controlled by electric signals emitted from a programme control device. The selection members have the job of placing the knitting tools passing them by in different states according to pattern so that, during the normal relative movement between the knitting tool carrier carrying said tools and a knitting cam assembly assigned to said carrier, said tools can be directed into tracks or paths according to choice which e.g. are responsible for the knitting types, knitting, non-knitting (welt position) and/or tuck. If only one individual selection member is assigned to each knitting system the electric signals must be supplied to said member at the operating rate of the knitting machine or at the speed at which they are passed from the knitting tools corresponding to the respective gauge of the knitting machine, the gauge being defined as the number of needles per inch. In modern circular knitting machines, the duration of such an operating cycle is circa 1 ms.
In order to make possible a reliable control of the knitting tools the selection members, which are predominantly the control magnets of electromagnetic systems, are made to operate very precisely timewise. Otherwise, loss of control times with the consequence of faulty control occurs. Electrically or electronically controllable knitting machines have therefore as a rule timing signal-generator devices which produce, at the operating rate of the knitting machine, successive timing signals consisting of short rectangular- or needle-pulses as a rule. These are superior to the usually longer control signals produced by the programme control device in such a manner that said signals appear at exactly predetermined and always identical intervals in time on the selection members. Timing signal-generator devices of this type are known in numerous embodiments and irrespectively of the manner in which the control signals are produced for the selection members (e.g. DE-AS 15 85 181, DE 21 29 851 C3, DE 20 26 584 B2, DE-OS 20 04 194).
In order to avoid the costs of a larger number of timing signal generators it is general practice furthermore to synchronise all the selection members of one knitting machine by means of the same timing signal generator. In addition, therefore, the precondition exists that the spacings of all the selection points, measured in the direction of movement, are identical to one another and correspond to an integral multiple of the needle distance so that the knitting tools adopt on all systems exactly the same position relative to the assigned selection member of a particular system when a timing signal appears. This has the result that in this case e.g. in a circular knitting machine the number of needles is chosen such that it is divisible by the number of systems without a remainder (e.g. 1440 needles, 72 systems, spacing of the systems 1440:72=20 needles).
In a circular knitting machine which can operate with the so-called three-way technique and which makes possible a choice between knitting, tuck, non-knitting on each system (e.g. DE 40 07 253 C2) there are arranged within one system or section of a system respectively two selection points arranged one behind the other in the direction of movement, the first selection point serving e.g. for directing at will the knitting tools into the non-knitting position or tuck position and the knitting tools, brought into the tuck position, at the second selection point are left if desired in this position or are transferred into the knitting position. As a rule it is thereby possible in fact to choose the spacings between the first selection points of all the systems such that they correspond to an integer multiple of the needle distance. For the spacings between the first and second selection points of each system this requirement is by contrast frequently unfulfillable since these spacings are dependent upon e.g. the geometry of the cam assembly curves, the construction of the selection members and upon other knitting technology facts. If an attempt were made however, to choose the mentioned spacings such that they correspond to integer numbers of needles both between the first selection points of all the systems and also between the first and second selection points of each system and are identical to one another respectively then this would generally only be realiseable for a specific gauge and/or the number of needles installed in total at the circumference of a needle cylinder or the like must be chosen such that unfavourable gauges E, not corresponding to the normal values, are produced (e.g. of E=15.8 instead of the normal value E=18). This disadvantage could be indeed avoided in part by selecting the spacings between the first and second selection points to vary depending upon the gauge. However this would require an accommodation at least of the knitting cam assemblies and the electromagnetic systems made preferably in one piece to the gauge or the needle distance provided in this particular case, which is undesirable on the grounds of simple, favourably priced manufacture.